Wonkeun Song, Gilsung Yoo, Gyu Yul Hwang, Young Uh
Ann Clin Microbiol 2016 September, 19(3): 59-64. Published on 20 September 2016.
Background: Extended-spectrum β-lactamase (ESBL)- producing Enterobacteriaceae are resistant to most β-lactam antibiotics except carbapenems. In recent years, infrequently isolated Enterobacteriaceae that produce carbapenemase pose a serious threat in the selection of appropriate therapeutic antibiotics. The rapid detection method of carbapenemase-producing Enterobacteriaceae (CPE) is necessary to prevent the spread of CPE into healthcare facilities.
Methods: One hundred clinical Enterobacteriaceae isolates (Klebsiella pneumoniae 40, Escherichia coli 40, others 20) showing susceptibility to carbapenems and positivity in the CLSI ESBL phenotypic test from November 2015 to March 2016 and 59 stocked Enterobacteriaceae isolates harboring resistance genes producing carbapenemase (K. pneumoniae 56, Enterobacter cloacae 2, E. coli 1; types of CPE: KPC 36, GES 12, NDM 6, VIM 2, OXA 2, IMP 1) were subjected to the RAPIDEC CARBA NP test (bioMérieux, France) and CPE phenotypic test using the modified Hodge test (MHT) and carbapenemase inhibition test.
Results: All of the 100 Enterobacteriaceae isolates with carbapenem susceptibility and ESBL positivity were negative on the RAPIDEC CARBA NP test and CPE phenotypic test. Of 59 stock CPE isolates, 53 and 42 showed positive results to the RAPIDEC CARBA NP test and MHT, respectively. The sensitivity and specificity of the RAPIDEC CARBA NP test for detecting CPE were 89.8% and 100%, respectively.
Conclusion: The RAPIDEC CARBA NP test is simple and produces a result within 3 hr. In conclusion, the test is a useful screen for detecting CPE because it shows high sensitivity and specificity for CPE detection.
[in Korean]
Young Ah Kim, Dongeun Yong, Yong Ha In, Hyung Soon Park, Kyungwon Lee
Ann Clin Microbiol 2016 September, 19(3): 65-69. Published on 20 September 2016.
Background: Sequence type 131 (ST131) O25b serogroup Escherichia coli, producing CTX-M type extended-spectrum β-lactamase (ESBL), is a major clone involved in worldwide pandemic spread in both community- and healthcare-associated infections. Recently, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) has become a routine tool for the identification of bacteria in many laboratories. This study aimed to assess the performance of MALDI-TOF MS for the screening of ESBL-producing E. coli ST131 in a rapid, inexpensive, and simple way.
Methods: A total 26 clinical E. coli, isolated from blood between 2013 and 2014, were used. The characteristics are ST131-O25b ESBL producers (n=6), ST131-O16 ESBL producers (n=4), non-ST131 ESBL producers (n=11), and non-ST131 non-ESBL producers (n=5). Specific biomarker peaks to distinguish the ST131 clonal group from others were investigated by MicroIDSys (ASTA, South Korea) and ASTA Tinkerbell 2.0 software.
Results: A peak at 9,713 m/z peak is useful to screen for ST131 E. coli, regardless of serogroup O25 or O16, showing a sensitivity of 100%, specificity of 56.2%, positive predictive value of 58.8%, and negative predictive value of 100% when using a relative intensity cutoff of 15%.
Conclusion: We can screen for ST131 E. coli using MicroIDSys (ASTA), MALDI-TOF MS in a rapid, inexpensive, and simple way. However, other confirmatory tests are needed to confirm ST131 E. coli due to the low specificity of this method.
[in Korean]
Min-Kyung So, Hae-Sun Chung, Chung-Jong Kim, Hee Jung Choi, Miae Lee
Ann Clin Microbiol 2016 September, 19(3): 70-76. Published on 20 September 2016.
Background: Blood cultures are essential in diagnosing and treating sepsis. There are several factors that affect the diagnostic yield of blood cultures such as the number of blood sampling episodes, the incubation period, the type and volume of culture media, and the amount of blood drawn. This study aimed to elucidate whether monitoring the volume of blood drawn with an educational intervention could affect the diagnostic quality of blood cultures.
Methods: We implemented quality monitoring for the blood volume drawn during blood culture testing for adults in an emergency room. We instructed the nurses in the emergency room to draw the optimal amount of blood and to reduce the number of blood culture sets from three to two. We analyzed and compared the amount of blood drawn, the rate of positive blood cultures, the contamination rate, and time to positivity (TTP) between 908 patients pre-intervention and 921 patients post-intervention.
Results: The amount of blood drawn increased from 0.7±0.3 mL per bottle (pre-intervention) to 6.5±1.7 mL per bottle (post-intervention) (P＜0.0001). The rate of positive blood culture post-intervention (12.14%) was higher than that pre-intervention (6.65%) (P＜0.0001). The contamination rate post-intervention (1.82%) was also significantly greater than that pre-intervention (0.60%) (P＜0.0001). Except for anaerobes, there was no significant difference in the distribution of microorganisms between the pre- and post-intervention periods. The TTP for anaerobe bottles post-intervention was significantly shorter than that of pre-intervention (16.1±16.3 versus 18.6±18.3 h).
Conclusion: This study suggests that continuing education about adequate blood volume and aseptic techniques is needed to increase the rate of positive blood cultures and reduce the contamination rate of blood cultures.
Eun Jeong Won, Yong Jun Choi, Soo Hyun Kim, Jong Hee Shin
Ann Clin Microbiol 2016 September, 19(3): 77-81. Published on 20 September 2016.
Mycobacterium abscessus was isolated from cultures of seven blood samples from a 64-year-old diabetic female who was admitted due to steroid-unresponsive adrenal insufficiency. The isolates were difficult to identify using the conventional commercial systems, VITEK 2 (bioMérieux, France) or MicroScan (Siemens Healthcare Diagnostics, USA), but were rapidly identified as M. abscessus by a matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS)-based Bruker Biotyper system (Bruker Daltonics, USA). Identification of M. abscessus was confirmed by a reverse hybridization-based assay (Genotype Mycobacterium CM/AS 12, Hain Lifescience) and direct sequencing of a heat-shock protein gene. After removal of her central venous catheter, the patient was successfully treated with a combination therapy comprising clarithromycin, amikacin, cefoxitin, and imipenem. Our findings demonstrate that MALDI-TOF MS can facilitate rapid and accurate identification of M. abscessus from blood cultures, which enables prompt administration of appropriate therapy following catheter removal.
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